Hearing aid



FIG. 1 is a perspective view of a hearing aid showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left elevational view thereof;

FIG. 5 is a right elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is another perspective view thereof.

The evenly-broken lines where present illustrate portions of the hearing aid that form no part of the claimed design. 

CLAIM The ornamental design for a hearing aid, as shown and described. 